NMRAL1 is a redox sensor protein that undergoes restructuring and subcellular redistribution in response to changes in intracellular NADPH/NADP+ levels. At low NADPH concentrations the protein is found mainly as a monomer, and binds argininosuccinate synthase (ASS1), the enzyme involved in nitric oxide synthesis. Association with ASS1 impairs its activity and reduces the production of nitric oxide, which subsecuently prevents apoptosis.